This is a city with plenty of height and density, after all. It has streetcars and other transit, plus bikes and pedestrians coursing through a grid. There are lots of innovation-economy jobs, too, as witnessed by the Amazon-fueled building boom all along Westlake Avenue. It’s as green a city as they come, and there’s a bustling foodie scene, thoroughly local and organic. Even the weather was nice.

Affordability and equity were among the most talked-about subjects at this year's APA conference.

It all sounds great, except for one additional characteristic of this fast-growing Pacific Northwest metropolis of 3.6 million: It’s rapidly becoming unaffordable.

The cost of housing in Seattle is already a crushing burden on household budgets. And officials here say it won’t be long before the median home price will catch up with Vancouver’s, another urban planning mecca across the border in British Columbia. Just how much does the median home cost in Vancouver these days? The latest estimate is $1.2 million.

The challenge of marbling affordability into the great urban renaissance of the last quarter centuryis not brand new, of course. But the evidence of social inequity in successful cities seems to have lately built to a fever pitch. Affordability and equity were among the most talked-about subjects at this year's APA conference, a part of virtually every discussion, from the future of struggling post-industrial cities like Detroit to vulnerable populations subject to the worst impacts of climate change.

It was standing-room only for two presentations in particular, by the city planners representing white-hot cities on either coast, New York and San Francisco. Attendees were peering in through the door to hear what possible policies and programs could make a difference.

Leading the buzz kill was Robert Hickey from the Center for Housing Policy, a division of the National Housing Conference, who quantified the scope of the problem—that incomes have simply not kept pace with housing costs. Citing a study of Chicago, Hickey said a growing number of families simply don’t earn enough to buy a typical home. Renters are the majority in 10 major cities from Miami to L.A., but the news is equally bad if not worse in that department: rents are up 40 to 80 percent. Households with severe housing cost burdens—shelter costs eating up the family budget and leaving little left over for anything else—have spread from low income to middle class.

Intensifying this dynamic is a supply and demand problem, as two groups—highly educated millennials and retiring boomers—compete with working-class residents for the same types of housing: smaller and efficient, and above all close to transit, jobs, and urban amenities.

Enter Purnima Kapur, the executive director of New York City’s Department of Planning, who attempted to explain how the city plans to achieve Mayor Bill de Blasio’s goal to add 200,000 affordable homes over 10 years. Demand for housing among low-income households in New York is twice as large as the supply. Two-thirds of New Yorkers rent, and within that group over 55 percent pay a third of their income for housing; 30 percent pay half.

The initiatives in New York, then, are all about increasing supply, both by preserving existing affordable homes—making sure they don’t disappear in redevelopment—and smoothing the way to create as much new housing as possible, as inexpensively as possible. That means zoning reform to reduce unnecessary impediments, such as removing outdated and costly minimum parking requirements for developers building near transit stations. The centerpiece initiative, however, is making what's called "inclusionary housing" mandatory—that is, making it a requirement that in new residential development, a significant portion, up to 25 percent, must be affordable.

John Rahaim, chief of the San Francisco Planning Department and formerly planning director in Seattle, said inclusionary zoning was also a major tool in the Bay Area. Developers have the option of paying a fee, providing the affordable housing on-site, building off-site, or dedicating a piece of land for the city to build affordable housing. San Francisco is also looking at the density bonus approach, where additional height is allowed in return for more affordability.

Betting it all on increasing the supply of housing is fraught, too.

But for all that effort, a total of 1,787 affordable units have been built since 1992, Rahaim said. “We should be building that many on an annual basis.” Currently, average rent for a two-bedroom apartment in San Francisco is $4,580 per month, and the median home purchase price is over $1 million. All the while, the Bay Area continues to grow, in people and jobs. Projections are for a population increase of 250,000 over the next five years. The city has already hit 40 percent of its 30-year projected job growth.

The trend toward micro-housing—super small living spaces, some with shared kitchens—hasn’t been the affordability solution once envisioned. Smaller isn’t necessarily cheaper in these hot markets.

Both cities are also exploring shared-equity housing and community land trusts, where typically a community non-profit acquires land through a long-term lease, and sells only the structures (thereby effectively taking the high cost of urban land out of the equation).

As the audience filed out of the room, they were left with the impression that their colleagues in New York and San Francisco were doing what planners do: systematically attacking a problem, working within the system, and setting long-range goals. They were laudably chipping away. But more than a few might have wondered whether these efforts would ever be enough.

The shortfall of affordable housing arguably would take 50 years to fill at the current rate of production in San Francisco—the very frustration expressed by Rahaim. It might take 25 years in New York City. But betting it all on increasing supply is fraught, too.It’s expensive to build in the city, and costlier still to build increased height and density without considering the needed infrastructure to support those kinds of environments.

Thinking differently about affordable housing can range from the fine-grained to the bigger picture. Seattle is a laboratory for prefabricated housing, including a modular, kit-of-parts project unveiled in the University District; if production costs can be kept down at urban infill sites, that’s an important first step. In a broader view, a more regional approach, with polycentric, high-density centers supported by transit, has the advantage of breaking out of the borders of the super-hot markets. Standing in some neighborhoods in San Francisco, Seattle, Chicago, Washington, D.C., New York or Boston, it’s hard to imagine that any part of them will ever be affordable again. But a better connected metropolitan region would open up possibilities in Malden, or Long Island or New Jersey, or Oakland and beyond.

This is the toughest of math equations, and the kind that won’t have a conventional answer. In khakis and the occasional Hawaiian shirt, America's urban planners are generally a cheerful and optimistic bunch, and rarely happier than when they can don the lanyards, network, and get out of the office for a few days. But they know all too well that everything else they do won’t count for anything if cities become places only the rich can enjoy. Most of them are heading home today. On affordability, they’ll be going back to the drawing board.